In an abandoned town, a young woman (Robbie) scavenges for food and other supplies. She wears home made protective clothing that protects her from the air. Once she has what she needs she heads out of town and into the nearby hills. Once she’s reached a certain distance she removes the protective clothing and continues on into a valley where it appears the air isn’t contaminated. She’s met by her dog, and together they reach her home, a farm where they live by themselves. There’s no electricity or gas, no working generator, but at least the weather is good, and the young woman has plenty of food.

It’s a lonely existence, but one borne out of necessity. The world has suffered a catastrophe, and the young woman, whose name is Ann, is a survivor, trapped/saved by the valley she lives in, which somehow acts as a natural barrier against whatever has happened. She’s already survived a hard winter where she nearly ran out of food, but she’s better prepared now, and is growing vegetables, tending chickens, and keeping a cow. She is becoming used to being alone, but still longs for human company.

One day her unspoken wish is answered. She discovers a man (Ejiofor), dressed in an anti-radiation suit, on the road near her home. He has a portable Geiger counter and is taking readings. When he realises that the area is unaffected he removes his suit. When Ann moves closer she finds him gone from the road and bathing at the base of a nearby waterfall. She implores him to get out, quickly, as the water is contaminated. Back at the farmhouse his sickness threatens his life, but thanks to drugs he has in his possession, Ann is able to save him from dying. The man, whose name is John, recuperates slowly, but he helps Ann as much as he can and even comes up with a plan to get the tractor going again. Ann and John begin to rely on each other, and as they do they become closer, forming a bond of mutual reliance and affection. And then they discover that there’s somebody else in the valley as well…

Those familiar with Robert C. O’Brien’s novel will know that there are only two characters in Z for Zachariah, and that the novel concerns itself with themes of science versus nature, and the clash of identities between Ann and John. But in Nissar Modi’s adaptation these themes are missing, and the viewer is left with themes of sexual jealousy and remorse, and John’s need to control the people around him (even if it’s just Ann). With the introduction of Caleb (Pine), Modi not only changes the nature of the struggle between Ann and John, he also changes irrevocably the tone of the movie and makes it less intriguing to watch.

What begins as a clever survivalist movie soon develops into a relationship drama where two people, who previously thought they were the only ones alive in their part of the world, adapt to coexisting again. It’s this section of the movie, where it’s just Ann and John and their relationship takes hold that offers the most rewards. As portrayed by Robbie, Ann is a gauche, likeable character who has a simple sincerity about her. It’s a good contrast to John’s anguished, bitter personality, and Ejiofor shows us the man’s deep-rooted insecurities slowly but surely, until the viewer is forced to realise that he’s not quite the “good man” that Ann believes he is. Pitted against her God-fearing background – her father built and preached in the nearby church – John treads carefully enough, but still leaves enough clues that he’s not fully to be trusted.

And it would have been great to see that dynamic play out with just the two characters, with Ann perhaps coming to terms with living with a man she’s attracted to but can’t trust. But again Modi doesn’t want to do that. Instead he introduces Caleb and makes the movie about sexual desire, a ménage à trois, with both John and Caleb circling each other and looking for ways to impress Ann. But where Caleb is supportive and charming, John reacts boorishly, and it’s at this stage of the movie where it becomes uncomfortably like a soap opera, and where the script struggles to maintain a clarity of purpose. At one point tells Ann that he’s okay with her being attracted to Caleb, that it’s okay if they want to “go and be white people together”. This remark is said in an almost offhand manner by John, but it’s indicative of the way in which the script suddenly lacks purpose. It’s a casual, racist comment, and should be powerful in its own way for being voiced by someone who’s black, but the script leaves it hanging, and never goes back to it.

With the last third hamstrung by needing to be more dramatic, the good work of the first hour is left behind. Pine is appropriately charismatic but as Caleb worms his way into Ann’s affections, the combination of the script, Pine’s performance, and Zobel’s now wayward direction, makes the whole thing seem implausible. All three elements fail to make a cohesive whole, and while the trio toil away at harnessing the energy of the waterfall to provide power for the generator, the viewer is left to watch things develop in such a way that the inevitable confrontation between John and Caleb lacks any bite, and the movie tries to end on a note of ambiguity that doesn’t really hold up.

Robbie, who is definitely an actress to watch at the moment, is very good as Ann, capturing the character’s innate trusting nature and revealing the pain she feels when that trust is abused. Ejiofor is equally good but John is a flawed character in more ways than one, and the script is less than subtle when it comes to revealing his motivations, leaving the actor to make the most of some very clumsy dialogue and direction. Along with Pine, Ejiofor seems to have been left to figure things out for himself in the final third, and Zobel’s influence wanes on the material the longer the movie goes on. By the end it’s almost as if the cast have directed themselves, but it’s at odds with what Zobel’s done up til then, and it shows.

Narrative and character disappointments aside, the movie at least looks absolutely beautiful, the New Zealand backdrops shot with an exquisite eye by Tim Orr, who did some equally impressive work on The World Made Straight (2015). It’s the one aspect of the movie that’s consistent throughout, and in conjunction with Robbie’s performance, makes the movie worth seeing, but both have to work hard to offset the slow pace made at the beginning, and the tired resolution at the end.

Rating: 6/10 – a movie that never quite gels into a satisfying whole, Z for Zachariah still has enough going for it to warrant a look; with all due respect to Pine, perhaps it’s also one to watch up until the actor makes his appearance – then you’ll have seen the best of it.